[14.03] The Rotation State of Small Rapidly Rotating Asteroids

C. W. Hergenrother, R. J. Whiteley (University of Arizona)

The smallest asteroids exibit rotational properties that are
distinct from more typical larger bodies. While all but two
asteroids larger than absolute magnitude (H) = 21.5 have
rotation periods greater than 2.2 hours, the opposite is
true for bodies smaller than H = 21.5. Of the 50+ small
asteroids with measured rotation periods, over 90% have
periods shorter than 2.2 hours. The periods range from 78
seconds (2000 DO8 and 2000 WH10) to greater than 6
hours for 2002 EC. A small but significant fraction of this
population are non-principal axis rotators.

The rapid rotation of small asteroids suggests that they are
coherent objects with intrinsic strength and not
strength-less rubble piles. Recent theoretical work has shed
doubt on this interpretation and argues that there is no
evidence for rubble pile structure among the asteroids
(Holsappe, K. A. 2005. Proc. Lunar Planet. Conf. 36th,
abstract 2329). We will show whether the objects in our
dataset are limited by strength-determined spin rates or
rubble pile-determined spin rates. The question of regolith
retention on such rapidly rotating asteroids will also be
addressed.

Funding for this research has been provided through a grant
from the NASA Near-Earth Object Observation program.